FIG. 23 is a block diagram outlining a conventional CAD/CAM system. The system comprises a central processing unit (hereinafter referred to as CPU) 1a, which includes a central processor 11 for executing control operations for controlling the entire system, a drawing definition section 12 for defining drawings for removal shape generation, a removal shape definition section 13a for defining removal shapes for path generation, a machining step definition section 14a for defining machining conditions, such as the specifications for coarse and finish machining, cutting extent and feed speed of the tool, from defined removal shape data, and a path generation section 15 for generating paths according to defined machining step data. Also, included is an input unit 2 for inputting force data and command data to the CPU, a display unit 3 for graphically displaying drawing data, shape data and paths according to the results of operation in the CPU, a storage unit 4 for storing program data and results of operations in the CPU 1a, and an output unit 5 for outputting the contents displayed on the display unit 3 to a printer or the like.
Now, a method of obtaining a finish shape shown in FIG. 9A by generating paths shown in FIGS. 10A-10D to 12A-12C on a work shape shown in FIG. 9B with the conventional CAD/CAM system, will be described with reference to a drawing element status view of FIG. 13A, a curve status view of FIG. 13B, removal shape Z direction division status views of FIGS. 14A and 14B, removal shape status views of FIGS. 15A-15H, 16A-16H and to 17A-17F, initial hole removal shape status views of FIGS. 18A and 18B, a Z direction cut extent uniformization status view of FIG. 19, and a flow chart of FIG. 23. A longitudinal line area in FIGS. 15A-15H and FIGS. 18A and 18B show removed portions, a heavy line area in FIGS. 15A-15H and FIGS. 18A and 18B show finish shape portions.
First, with reference to FIGS. 13A, 13B and 23, lines a1 to a7 shown in FIG. 13A are defined by inputting commands for defining the lines a1 to a7 together with X-Y coordinates of end points t1 to t6 of the lines a1 to a7, X-Y coordinates of center points t7 and t8 of the lines a6 and a7 and radii r1 and r2 of the lines a6 and a7 from the input unit 2. Also, "curves" C0 to C4 shown in FIG. 13B are defined by inputting a command for extracting the curve C1 from the lines a1 to a4, a command for extracting the curve C2 from the lines a1, a2, a4 and a5, a command for extracting the curve C4 from the line a7 and a command for extracting the curve C0 from the lines a1 to a3 and a5 from the input unit 2 (step S51: drawing definition in FIG. 24).
Then, a removal shape V11 shown in FIG. 15A is defined by inputting a command for defining the removal shape V11 from the input unit 2. The command would be for performing machining from a machining surface height Z0 shown in FIG. 14A to the machining surface height Z1 plus Z direction finish margin Cz1, together with the machining surface height Z1 and Z direction finish margin Cz1. Also, like the removal shape V11, removal shapes V12 to V14 shown in FIGS. 15C-15H, shapes V21 to V24 shown in FIGS. 16A-16H and shape V31 to V33 shown in FIGS. 17A-17F are defined by inputting data of the curves C1 to C4, machining surface heights Z2 to Z4 and Z direction finish margins Cz2 t Cr3 (step S52: removal shape definition in FIG. 4).
Further, a machining step K11 shown in FIG. 21 is defined by inputting several lines from the input unit 2. The input are command for defining the machining step K11, a helical or parallel line machining pattern of path P11 shown in FIG. 10A generated for the removal shape V11, a radial direction cut extent Pr11 shown in FIG. 10A, a Z direction cut extent Pz1 and radial direction finish margin Cr1 shown in FIG. 19, a Z direction finish margin Cz1 shown in FIGS. 14A and 14B and a machining directions d11 of the path P11 shown in FIG. 10A.
Like the machining step K11, machining steps K12 to K14, K22 to K24 and K31 to K33 are defined by inputting machining patterns of paths P12 to P14 shown in FIGS. 10A-10D and paths P21 to P24 shown in FIGS. 11A-11D, radial direction cut extents Pr12 to Pr14 and Pr21 to Pr24, radial direction finish margins Cr2 and Cr3 and machining directions d12 and d13 shown in FIGS. 10A-10D and s22 to d24 shown in FIGS. 11A-11D.
With respect to the coarse machining removal shape V14 shown in FIG. 15G, a machining step K1 shown in FIG. 21 is further defined by inputting the X and Y coordinates of the machining position H1 of the initial hole removal shape I1 shown in FIGS. 18A and 18B, the machining surface height Z2 plus Z direction finish margin Cz3 shown in FIG. 15G as the machining surface height Z and the machining surface height Z2 plus Z direction finish margin Cz2 as the machining surface height Z (step S53: machining step definition).
Then, machining path generation commands for generating the paths P11 to P14, P21 to P24 and P31 to P33 from the machining steps K11, K12, K1, K13, K14, K21 to K24 and K31 to K33, defined in the step S4a, are input from the input unit 2 (step S54: machining path generation commanding).
The path generation section 15, receiving the above machining path generation commands, generates the path P11 for the machining step K11 according to the radial direction cut extent Pr11, Z direction cut extent Pz1 and machining direction d11, designated in the step S4a. Likewise, the section 15 successively generates the paths P12, P1, P13, P14, P21 to P24 and P31 to P33. When it has generated the paths up to the lowest surface Z height Z4, it ends the process (step S55: path generation).
With the conventional CAD/CAM system having the above construction, however, it is necessary to define the removal shape by dividing the work shape in the radial and Z directions for each machining step. In addition, it is necessary for each removal shape to input the radial and Z direction cutting extents and finish margins, helical, parallel line or like path pattern, machining direction data concerning the path, Z direction machining surface height and machining depth concerning the initial hole, and offset direction and offset amount of the removal shape contour curve. It is time-consuming to input the above shape data and machining data. In addition, the optimum input value determination and machining step design require skill and thus lead to inferior operation efficiency.